The present invention relates to an apparatus and method for treating wood chips and particularly to a control apparatus which prevent damage to downstream treating and destructuring apparatus due to the presence of tramp metal
In connection with the papermaking process, logs are debarked and chipped and the wood chips are treated to release individual cellulose fibers for the preparation of paper formation stock.
One device for treating the chips is a chip slicer which includes a rotor operating within a drum wherein oversized chips are forced against knives and sliced to an acceptable thickness. Another form of chip processing device is disclosed in U.S. Pat. No. 4,953,795 wherein chips are passed between a pair of closely operating rolls which supply compressive forces to the chips to cause the chips to crack in the thickness dimension as compressive force is applied to the chips.
Common to chip processing devices is a conduit for handling the chips leading to the chip processing device and a flow stream of chips flow through the conduit controlling a uniform supply of wood chips. In one form of such conduit, chips are carried pneumatically past a rotary valve which regulates the flow. Common to all chip processing devices is the risk that tramp metal will become embodied in the chip flow stream and such tramp metal has a devastating effect on the chip processing apparatus, breaking knives or damaging operating surfaces to the extent that the machine must immediately be shut down and the resultant damage repaired. Yet, for satisfactory commercial processing of chips, it is desirable, if not essential, that the machine continue operating at a relatively uniform speed of operation to be able to accommodate the supply of chips which is continually fed to the chip processing apparatus.